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EXT_LFx pin of ADV7344


There are some questions about EXT_LFx pin of ADV7344.

The datasheet says that 12nF, 150nF capacitor and 170ohm resistor should be connected to EXT_LFx pin.

The issue occurs that mechanical shock by external makes some abnormal picture.

So, they tried to reduce the capacitor value(12nF->1.2nF, 150nF->15nF), then the issue is fixed.

Can ADV7344 accept above reduced capacitor value?

Best regards.


These are not the recommended values and the device has not been tested with these values.  Test specifications only apply to the recommended values. You can use 169 1% resistor instead of 170 Ohms

Yes, vibrations can effect PPL's via acoustic vibrations in the PLL filter caps.  Possible solutions

1) Stiffen the board near the caps, i.e. change the board resonant frequency so vibrations don't effect the cap

2) rotate the cap 90 degrees in the layout.  This effect how resonance couples into the cap.

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